1. Field of the Invention
The present invention relates, in general, to a method for removing cholesterol from milk and cream and, more particularly, to use of .beta.-cyclodextrin in removing cholesterol from milk and cream.
2. Description of the Prior Art
Some milk products are high in cholesterol content. For instance, cholesterol is usually present at an amount of 219 mg per 100 ml in butter, 110 mg in cream cheese, and 105 mg in ice cream. Because these milk products are manufactured by using, as a base material, cream, which is rich in cholesterol (100 ml of cream with a fat content of 36% contains approximately 125 mg of cholesterol), the cream is a source of cholesterol for the milk products.
Milk contains a small amount of cholesterol (cholesterol as small as 13.14 mg is present in 100 g of the milk 3.6% in fat content). Thus, it is nutritionally beneficial for the average person to drink milk which normally contains cholesterol. However, cholesterol-free milk is needed for medical patients who must avoid the ingestion of cholesterol, for example, patients suffering from cardiac diseases, such as hypertension, arteriosclerosis, coronary arteriosclerosis, etc. Cholesterol-free milk is also used as a material for the production of cholesterol-free yogurt or cheese and is one of the most favorite foods to those who refuse to eat animal fat owing to the fear of adult diseases.
.beta.-Cyclodextrin (hereinafter referred to as ".beta.-CD"), a cyclic polysaccharide consisting of 7 glucose residues, is used to remove cholesterol. Because its central portion is a circular hydrophobic space similar in diameter to a cholesterol molecule, .beta.-CD can well bind cholesterol, which is non-polar. Particularly, .beta.-CD easily absorbs cholesterol at a temperature as low as or lower than 4.degree. C., so that it is effective in keeping the quality of milk. In addition, .beta.-CD can be easily separated by virtue of its low solubility. Further, it has the advantages of being inexpensive and safe to the human body and being permitted to be used as a food additive in many countries.
Japanese Pat. Laid-Open Pub. No. 04168198 relates to a removing method of cholesterol from cream, disclosing that 20 g of cream with a water content of 50% is added with 1.2 g of .beta.-CD, stirred at 30.degree. C. for 60 min, warmed and centrifuged to isolate a cream line. The maximal removal of cholesterol was allegedly 84.9%.
Another condition for removing cholesterol was suggested (J. of Dairy Science, Vol. 76, Supplement 1, Abst. No. D158). According to this, the treatment of cream with .beta.-CD while stirring at 40.degree. C. for 120 min is written to show a removal efficiency of 83% in maximum.
These conventional processes, however, may cause a degradation in the product quality because the stirring is carried out at too high temperatures as well as for too long times. Another problem of the conventional processes is that the maximal removal efficiency is low.
While approximately 80% of the cholesterol of milk is present in fat globules, the rest is in milk serum. Thus, in order to remove cholesterol from milk at a maximum, milk is needed to be homogenized before the removal.
Cholesterol removal from milk is disclosed in International Patent Laid-Open No. WO 93/05084. According to this patent, 10 ml of homogenized milk is added and mixed with 200 mg of .beta.-CD or .beta.-CD polymer at 15.degree. C., stirred for 30 min and centrifuged at 4,000.times.g for 15 min at 4.degree. C. to separate cream and milk. The supernatant cream is subjected to cholesterol assay. This technique may also cause degradation of the product quality owing to the same reasons as in above: too high temperature and too long time for the stirring. In addition, too much .beta.-CD is used. The too fast centrifugation brings about the separation of cream line, deteriorating the product quality. This requires re-homogenization of the milk, resulting in a too long production procedure and an increase in production cost.